Method and apparatus for processing a preform for a rim, and rim

ABSTRACT

A method for processing a preform for a rim wherein a ring-shaped rudimentary metal rim edge ( 5 ) is clamped in a slit ( 13 ) moving along the circumferential edge of the rim edge ( 5 ) between a profiled outer surface ( 8 ) of a mandrel ( 7 ) and a profiled outer surface ( 11 ) of a profiling roller ( 9 ), wherein the slit ( 13 ) is wedge-shaped and wherein an angle (a) included by the centerlines ( 6, 10 ) of mandrel ( 7 ) and profiling roller ( 9 ) is reduced, propelling material of the rudimentarily formed rim edge ( 5 ) to a wider portion of the slit ( 13 ). The invention also relates to an apparatus for processing a preform for a rim, and a rim.

The invention relates to processing a preform for a rim.

In the manufacture of rims, it is known to process a ring-shaped, rudimentarily formed metal rim edge to a configuration which corresponds more closely to a ready rim bed with regard to shape and thickness. Such a rudimentary rim edge forms a preform for the rim, often together with a center portion forming the “star” of the rim. Such a preform may, for instance, be forged, but may also be cast.

EP 0 680 794 relates to an improvement of the spin forging process known per se, where it is proposed to have the tiltably arranged mandrel cooperate with a rotatably arranged profiling roller instead of, as conventional, with a stationary bed. Between a part of the profiling roller and the tiltably arranged mandrel, a closing slit is formed in which the rim material is processed by flowing. Another part of the profiling roller profiles a lower portion of the rim to be formed in a conventional manner by pressing.

The publications JP 58 05513, DE 464 772, JP 10 005887 and WO 99/67042 relate to CNC operations where the form information is at least partly stored in a computer program, and mandrel and roller therefore do not determine the basic profile of a rim.

The publication US 2005/274015 relates to a manufacturing process for a rim, where a mandrel and a roller cooperate. Here, the cooperation involves a local profiling operation, which is part of multiple preprocessing and final processing steps for profiling the basic shape of the rim.

The publication DE 464 772 describes an apparatus for bending plate material with a pressure tool.

In PCT/US99/14437, it is described that the rudimentarily formed rim edge is stretched, thinned and profiled on the outer surface of a mandrel in a so-called flow-spinning operation with the aid of a pressure disc translating along the outer surface of the mandrel. Utilizing a rudimentarily formed rim edge, the forging or casting of larger material volumes for, for instance, rims with larger diameters can be facilitated, while the material properties of the rim bed can be of a high quality due to the flow-spinning operation.

A drawback of the known method is that it is relatively complex, expensive and time-consuming, and that sometimes final processing is needed. In particular, the pressure disc can cause a spiral pattern in the rim bed which needs to be leveled in final processing.

The invention contemplates an alternative, with which, while maintaining above-mentioned advantages, above-mentioned disadvantages can be obviated.

To this end, the invention provides a method for processing a preform for a rim, wherein a ring-shaped rudimentary metal rim edge is clamped in a slit moving along the circumferential edge of the rim edge between a profiled outer surface of a mandrel and a profiled outer surface of a profiling roller, wherein the slit is wedge-shaped and wherein an angle included by the centerlines of mandrel and pressure roller is reduced, propelling material of the rudimentary rim edge to a wider portion of the slit by pivoting the profiling roller with respect to the mandrel.

By receiving the material of the rudimentarily formed rim edge in this manner in a closing nip between two profiled outer surfaces, the stretching, thinning and profiling of the rudimentary rim bed can be carried out quickly and simply in one processing step, while the creation of a spiral pattern can be avoided. During narrowing of the slit, then the contact surface between the material of the rudimentarily formed rim edge and the outer surface of the pressure roller is increased. The mandrel and the roller then together form the basic profile of the rim edge to be formed.

Upon reducing the angle, material of the rudimentarily formed rim bed is displaced substantially in axial direction, in particular in a direction away from the central center portion of the preform.

By maintaining a positive included angle during the processing, it can be achieved that the flow direction of the material is uniform.

By pressing an edge of the outer surface of the profiling roller into the material of the rudimentarily formed rim bed during a first part of the processing, during the further reduction of the included angle, the flow of the material can be forced into one desired direction. In particular, it can thus be avoided that, on the preform, between the “star” and the rudimentary rim bed, a constriction needs to be formed, which makes the forging or casting of the preform simpler.

Preferably, to this end, the distance between mandrel and profiling roller is reduced by translating mandrel and/or profiling roller. Preferably, here, the profiling roller is translated substantially transversely to its centerline in the direction of the mandrel, so that the edge of the outer surface of the profiling roller can penetrate the material of the rudimentary rim bed.

The invention also relates to an apparatus for processing a preform for a rim, comprising a mandrel with a profiled outer surface arranged rotatably about a centerline and a profiling roller with a profiled outer surface arranged rotatably about a centerline, while, during use, a slit can be realized between the outer surfaces for receiving a ring-shaped rudimentarily formed metal rim edge therein, while the slit is wedge-shaped and while the profiling roller is arranged pivotally with respect to the mandrel and while, by adjustment of the profiling roller with respect to the mandrel, the angle included by the centerlines of mandrel and profiling roller can be reduced.

The invention also relates to a rim formed with the aid of above-mentioned method and/or apparatus.

Further advantageous embodiments of the invention are shown in the subclaims. The invention will be explained in more detail on the basis of a non-limiting exemplary embodiment of the invention, which is shown in a drawing.

In the drawing, with reference to FIGS. 1-6, in cross-sectional side elevational view, a number of successive steps of processing the preform of the rim are schematically shown.

In the Figures, same or corresponding parts are designated by the same reference numerals.

FIGS. 1-6 show an apparatus 1 for processing a preform 2 for a rim.

The preform 2 comprises a central center portion 4 forming the “star” of the rim, and a ring-shaped, rudimentarily formed rim edge 5 extending along the outer circumference thereof.

In this exemplary embodiment, the preform 2 is manufactured from light metal, for instance from an Al Si 7 Mg or AA 6061 alloy.

The apparatus 1 comprises a mandrel 7 arranged rotatably with respect to centerline 6. The mandrel 7 has a profiled outer surface 8.

The apparatus 1 further comprises a profiling roller 9 which is arranged rotatably with respect to a centerline 10. The profiling roller 9 is provided with a profiled outer surface 11. The outer surface 8, the mandrel 7 and the outer surface 11 of the profiling roller together form the basic profile of the rim edge to be formed.

During the processing, the preform 2 is pressed on the mandrel 7 with the aid of a stick 12, and lifted from the mandrel 7 therewith after the processing.

The profiling roller 9 and the mandrel 7 are, as will be explained hereinafter in more detail, arranged to be adjustable with respect to each other, so that, between the outer surfaces, a wedge-shaped slit 13 can be realized in which the rudimentarily formed rim edge 5 can be received.

By adjustment of the mandrel 7 and the profiling roller 9 with respect to each other, the angle α included by the centerlines 6, 10 of mandrel 7 and profiling roller 9 can be reduced, so that the slit 13 included by the outer surfaces 8 and 11, respectively, is narrowed during processing.

In this exemplary embodiment, the profiling roller 9 is arranged to be translatable transversely with respect to its centerline 10 in the direction of arrow P1, so that an edge 7 of the outer surface 11 can be pressed into the material of the rudimentary rim edge 5 during a first part of the processing.

Further, the profiling roller 9 is arranged pivotally with respect to the mandrel 7, such that, by pivotal movement of the profiling roller 9 in the direction of the arrow P2 with respect to the mandrel 7, the angle α included by the centerline 10 of the profiling roller and the centerline 6 of the mandrel can be reduced. Thereby the slit 13 included between the outer surfaces 8 and 11, respectively, can be narrowed. The angle α is acute and preferably has an initial value of less than about 45° and a final value of more than 0°, in particular about 30°-5°, respectively.

Thus, the ring-shaped, rudimentary metal rim edge 5 can be clamped in a slit 13 moving as a result of relative rotation between mandrel and profiling roller along the circumferential edge between the profiled outer surface 8 of the mandrel 7 and the profiled outer surface 11 of the profiling roller 9.

Here, the slit 13 is wedge-shaped. Due to reduction of the slit angle included between the outer surfaces 8 and 11, respectively, material of the rudimentarily formed rim edge 5 is propelled to the wider, open portion 15 of the slit.

Upon reducing the angle, the material is then moved substantially in axial direction, away from the “star” 4 of the preform 2. During narrowing of the slit 13, the contact surface of the material of the rudimentary rim edge 5 and the outer surfaces 8, 11 is increased. In the final position, the rudimentary rim edge 5 is stretched, thinned and profiled to a rim bed 16. Thus, in one processing step, from any rudimentary preform 2, a complete rim 5 is formed, which hardly needs any final processing.

During the processing, most preferably, a positive angle α is maintained, so that, during the whole processing, the material of the rudimentary rim edge 5 keeps on flowing to the wider portion 15 of the slit.

The invention is not limited to the exemplary embodiment shown herein. For instance, multiple pressure rollers may be used. Such variants will be readily apparent to a skilled person and are understood to be within the scope of the invention as set forth in the following claims. 

1. A method for processing a preform for a rim, wherein a ring-shaped rudimentary metal rim edge is clamped in a slit moving along a circumferential edge of the rim edge between a profiled outer surface of a mandrel and a profiled outer surface of a profiling roller, wherein the slit is wedge-shaped and wherein an angle included by the centerlines of the mandrel and the profiling roller is reduced, and propelling material of the rudimentary metal rim edge to a wider portion of the slit by pivotal movement of the profiling roller with respect to the mandrel.
 2. A method according to claim 1, wherein, a contact surface between the material of the rudimentary metal rim edge and the outer surface of the profiling roller is increased.
 3. A method according to claim 1, wherein, a positive included angle is maintained.
 4. A method according to claim 1, wherein, during the reduction of the included angle, material of the rudimentary metal rim edge is displaced substantially in an axially outward direction with respect to the ring-shaped rim edge.
 5. A method according to claim 1, wherein an edge of the outer surface of the profiling roller is pressed into the material of the rudimentary rim edge.
 6. A method according to claim 5, wherein the distance between mandrel and profiling roller is reduced by translation of mandrel and/or pressure roller with respect to each other.
 7. A method according to claim 6, wherein the profiling roller is translated substantially transversely to its centerline in the direction of the mandrel.
 8. An apparatus for processing a preform for a rim, comprising a mandrel with a profiled outer surface arranged rotatably about a centerline and a profiling roller with a profiled outer surface arranged rotatably about a centerline, wherein, during use, between the outer surfaces, a slit is realized for receiving a ring-shaped rudimentarily formed metal rim edge therein, wherein the slit is wedge-shaped and wherein the profiling roller is arranged pivotally with respect to the mandrel and wherein, by adjustment of the profiling roller with respect to the mandrel, the angle included by the centerlines of mandrel and profiling roller can be reduced.
 9. An apparatus according to claim 8, wherein the profiling roller is arranged so as to be translatable substantially transversely with respect to the centerline.
 10. A rim manufactured according to the method of claim
 1. 